There's a nice little biography of Joseph Greenstein, AKA "The Mighty Atom":
Some of the tales may or not be true, of course,
but it is fun to read.
And don't forget Slim "the Hammer Man" Farmar, Greenstein's only student-protege:
In turn, the contemporary representative of this kind of body work (called "isometric strength training") is Dennis Rogers. Slim Farmar being his mentor. Rogers had an online "museum" dedicated to the Mighty Atom, but it appears to be defunct. He has a website/forum -- Tough Guy -- that still appears to be somewhat active:
Actually, that title belongs to Joseph Greenstein, the Mighty Atom
, who jumped ship in Yokohama and trained in some kind of jujutsu there, one of the first non-Japanese ever to do so, in, IIRC, 1905. What isn't mentioned in the Wikipedia article is that the training regimen he followed as a kid, learned from the circus strongman, included a lot of specific breathing exercises. (And my favorite "feat of strength" listed in the article is - "Beating up 18 Nazis with a baseball bat." - times were different then - the judge praised him for it).